In 2009 , the FACS Core Lab provided service to 30 NCI labs or branches and 3 other institutes. From these labs, there were 86 principal investigators using the FACS Core Facility. These labs, with the number of principal investigators and the number of individuals using the FACS Core in parentheses, are: BRL (2 PIs, 2 users),CCBB (6,28) Dermatology Branch (2,4), Genetics Branch (4,12), HAMB (1,1), LBMB (2,6), LCB (3,6), LCBG (12,39), LCMB (6,24), LCO (5,15), LCP (1,3), LEC (2,11), LHC (3,14), LICB (3,13), LM (4,7), LMB (6,20), LMP (5,18), LRBGE (1,4), LTIB (3,5), MBTL (4,10), Metabolism Branch (1,1), Medical Oncology Branch (4,9),MTP (1,1), Neuro-Oncology Branch (1,1), OD (1,1), Pediatric Oncology Branch (1,7), Radiation Oncology Branch (1,4), Surgery Branch (2,5), Urologic Oncology Branch (1,1), NCI-Frederick (1,1), NHLBI (1,1), NIAMS (1,1), and NIDDK (1,1). From these labs, 247 scientists have used the FACS Core in FY2008 and of these, 57 were new to the Core lab this past year. Identifying and studying cancer stem cells is one of the major research areas of the FACS Core Lab users. A number of NCI labs are using flow cytometry and fluorescence-activated cell sorting to identify and sort the cancer stem cell by membrane antigen expression using monoclonal antibodies or with a functional assay involving active membrane substrate transport. Investigators in CCBB, MBTL, LEC, LHC, LCBG, LM, and Surgery Branch are studying cancer stem cells from breast, ovarian, hepatic, thyroid, pancreatic, and lung carcinomas. The LSRII flow cytometer, the FACS Vantage cell sorter, and the new special order FACS Aria, because each is equipped with a UV laser, are frequently used for these assays. Transfection of cells with genes expressing fluorescent reporters is a technique used by the majority of the labs using the FACS Core. The FACS Core cytometers and cell sorters have been equipped with specific lasers to allow detection and sorting of cells labeled with any of the green, yellow, blue, red, and UV fluorescent proteins or with combinations of these fluorescent reporters. Sorted transfected cells are used to prepare protein, DNA, and RNA that can be used in Western blotting and microarrays. Sorted cells are also used to determine effects of siRNA, to look at signaling proteins, or may be further passaged to create stable cell lines. Fluorescent reporter proteins may also be linked to luciferase. Tumor cell lines have then been sorted based on their expression of green or red fluorescent protein to establish cell lines with high levels of luciferase. These cells have then been used to establish tumors in mice and to image metastasis. In addition to the 1 co-authored publications, 15 additional publications this year have included work done in the FACS Core and/or acknowledgments of FACS Core participation.